Nod - that's what I was thinking. I expect it's often the connectors that deteriorate so perhaps moving them around while plugged in would tell me. Seems like a useful tool to have around.

i've used a treedix tester like this. the edition with many led lights, not the one with a screen.

wiggle the cables around to see if and when any of the lights flicker, indicating a bad or broken connection. i've found a few bad cables that would intermittently fail.

That's great. Thank you for the feedback - I ordered one just now.